Summary
Phenylephrine is primarily used as a decongestant, vasopressor, and mydriatic agent. It has poor oral bioavailability (~38%) due to extensive first-pass metabolism. The FDA has questioned its efficacy as an oral decongestant, with studies showing it performs no better than placebo at standard 10 mg doses. It is significantly less effective than pseudoephedrine but remains available over-the-counter because it cannot be used to synthesize methamphetamine. Phenylephrine does not cross the blood-brain barrier and has no central psychoactive effects.
Dose Information
| ROA | Light | Common | Strong | Heavy |
|---|---|---|---|---|
| Nasal | 0.25-0.5mg | - | - | - |
| Ophthalmic | 1-2.5% | - | - | - |
Light
Common
Strong
Heavy
Onset, Duration & After-effects
| ROA | Onset | Comeup | Peak | Offset |
|---|---|---|---|---|
| Oral | 15-30 min | 30-60 min | 1-2 hrs | 1-2 hrs |
| Intravenous | - | 1-2 min | 5 min | 10-15 min |
| Nasal | 5-10 min | 10-20 min | 15-30 min | 1-2 hrs |
| Ophthalmic | 1-5 min | - | 30-60 min | 2-4 hrs |
Tolerance
Build-up
develops rapidly after a single use (serotonergic psychedelic)
Reset
7–14 days for baseline
Effects
Positive
- Nasal decongestion
- Stimulation
Negative
- Vasoconstriction
- Increased blood pressure
- Pupil dilation
- Headache
- Restlessness
- Increased heart rate
- Insomnia
- Reflex bradycardia
Positive
- Alertness enhancement
- Euphoria
- Wakefulness
- Cognitive euphoria
- Motivation enhancement
- Focus enhancement
Negative
- Anxiety
- Talkativeness
- Time distortion
- Thought acceleration
Positive
- Increased music appreciation
- Tactile enhancement
- Increased libido
- Color enhancement
Negative
- Light sensitivity
- Appetite suppression
- Dehydration
- Disinhibition
- Drifting
- Dulled perception